Heat exchanger and method of manufacturing

ABSTRACT

The invention relates to a heat exchanger comprising at least one pipe ( 1 ) and at least one lamella ( 2 ), for exchanging heat between a first coolant that flows through the pipe ( 1 ) and a second coolant that wets the heat exchanger under the influence of centrifugal forces in order to be cooled and to be available to further cool a rotating machine element ( 3 ) that is situated in a housing ( 4 ), 
     where the heat exchanger is of approximately ring-shaped design, essentially surrounds the rotating machine element ( 3 ) and is integrated into the housing ( 4 ).

The invention relates to a heat exchanger, comprising at least one pipe and at least one lamina, for exchanging heat between a first coolant and a second coolant, which serves to cool a rotating machine element. In addition, the invention relates to a suitable method of manufacturing the heat exchanger.

Numerous heat exchangers are known from the existing art, and are often designed in a ring shape. In most applications, ring-shaped heat exchangers serve to cool a first coolant flowing through the flat piping of the heat exchanger by means of cooling air that is blown by a fan or the like from inside to outside (or vice versa) through cooling ribs situated between the flat pipes.

Likewise in most cases the flat pipes have been bent on their narrow sides, so that a plurality of flat pipes can be situated side-by-side and the laminae or the cooling ribs for the radially flowing cooling air can be placed between them. One example among numerous others was described in DE 37 21 257 C2.

A ring-shaped heat exchanger has also already been proposed, whose flat pipes have been bent on their wide sides, which is more easily accomplished in terms of production technique. In this case, however, the cooling air flows axially through the laminae situated between the flat pipes. One such example can be found in DE 3 104 945, FIG. 4.

Ring-shaped heat exchangers have often been equipped with round or slightly oval pipes, which are easier to bend than flat pipes. The lamellae there are usually flat ribs that have openings through which the pipes have been inserted before being bent. With round pipes the surfaces involved in the heat exchange are smaller than with flat pipes, which worsens their efficiency.

Rotating machine elements may be for example clutches or brakes that have a need for cooling. Torque transmitting elements have been addressed for example—frequently referred to as wet clutches—that run through a coolant sump, in most cases containing oil, and that fling the coolant away by their rotation. The coolant then runs down the wall of the housing, for example, back into the sump, and there can cool down. There are also numerous publications in this field.

The object of the invention is to provide a heat exchanger for cooling a coolant flung off by a rotating machine element, with which efficient cooling can be achieved. The intent is to contribute to the ability to increase the transmission of power by means of the machine element while keeping the construction space small.

The solution according to the invention in reference to the heat exchanger derives from the features of claim 1. The manufacturing method according to the invention is found in claim 11.

The heat exchanger comprises at least one pipe, preferably a flat pipe, and at least one lamina, and serves to exchange heat between a first coolant, which flows through the flat pipe, and a second coolant, which wets the heat exchanger under the influence of centrifugal forces. The second coolant is cooled thereby and is available to further cool a rotating machine element that is situated in a housing, whereby the heat exchanger is of approximately ring-shaped design, essentially surrounds the rotating machine element, and is integrated into the housing.

A heat exchanger designed and situated in this manner enables active and effective cooling of the second coolant, and thus contributes both to the ability to increase the transmission of power by means of the rotating machine element and the ability to reduce the quantity or space requirement of the second coolant while maintaining the same performance. The greater quantities of heat loss that occur with greater transmission of power, caused chiefly by friction, are transferred effectively to the first coolant and dissipated. The space requirement of the ring-shaped heat exchanger in the housing is relatively small. The expression “ring-shaped” as used in the present proposal is not intended to mean only circular, but rather to include any contour that is suitable for essentially surrounding the rotating machine element. About half of the circumference of the machine element at least should be enclosed by the heat exchanger. Preferably, however, the heat exchanger extends around at least nearly the entirely circumference of the machine element and is integrated into the latter's housing.

According to an advantageous aspect, it is further provided that at least one flat pipe is designed to be bent on its wide sides, with the lamina being situated on the wide side that faces inward. This is the side that is wetted by the second coolant. It is known to be simpler to bend flat pipes along their wide sides. The wide sides of the flat pipe are thus situated approximately parallel to the axis of rotation of the machine element.

It is readily possible to employ a plurality of flat pipes lying side-by-side, bent on their wide sides.

It is also possible to employ one or more flat pipes with ribs situated in the intervals between the flat pipes, with the flat pipes bent on their narrow sides.

Another aspect provides that the lamina is provided with a jacket provided with openings, which extends approximately parallel to the wide side of the flat pipe and covers the lamina. The jacket is for example a sheet metal strip. That increases the intensity of the heat exchange.

The openings are designed and situated so that the second coolant can flow as far as the lamina and as far as the wide side of the flat pipe, and can flow out of the lamella again. The coolant can also flow out on the narrow sides of the lamina or at its longitudinal edges, because the edges do not have to be enclosed by the covering. As a result, the retention time of the second coolant in the lamina or on the flat pipe is prolonged, and it can be cooled more intensively.

The second coolant flows into a sump or similar collecting pan, in which it can be reached by the rotating machine element.

Situated on at least one end of the at least one flat pipe is an end chamber for supplying or carrying off the first coolant.

Preferably end chambers are provided on both ends of the at least one flat pipe.

Furthermore, it is also advantageous if straps or similar connecting elements are provided on at least one of the end chambers, in order to connect the two end chambers together.

It is advantageous in terms of manufacturing if the at least one flat pipe, in which the first coolant flows, is either a soldered or welded flat pipe with an inner insert or a flat pipe manufactured by means of an extrusion process. The lamina has a wave-type contour, with numerous cuts at offset positions in the wave flanks, with the waves running perpendicular or obliquely to the direction of extension of the pipe. Such laminae are known from the field of “oil cooling.” This lamina acts in conjunction with the jacket described above. The jacket is preferably a sheet metal covering that is soldered together with the lamina and the pipe.

The method for manufacturing a heat exchanger from at least one flat pipe and at least one lamina contains the following procedural steps:

-   a) a lamina is placed on the wide side of the at least one flat     pipe; -   b) end chambers are affixed to the end of the flat pipe; -   c) the parts are joined by metal material; -   d) a bending procedure is performed in order to produce a     ring-shaped heat exchanger; -   e) the ring-shaped heat exchanger is inserted into a housing in     order to cool the coolant of a rotating machine element.

Step a) can include placing a jacket with openings on the lamina.

The end chambers can be joined with each other in the course of assembly.

The invention will be described below in an exemplary embodiment with reference to the accompanying drawings. Additional advantageous features and effects can be contained in this description.

FIG. 1 shows the principle of how the heat exchanger is integrated into the housing.

FIG. 2 shows three details from the heat exchanger with different pipes.

FIG. 3 shows the ring-shaped heat exchanger in perspective representation.

FIGS. 4 and 5 show details in the area of the end chambers of the heat exchanger.

FIG. 6 shows three possible arrangements of the lamina.

FIG. 7 shows possible designs of the jacket.

The heat exchanger shown in the exemplary embodiment is made up of a single flat pipe 1 and a lamina 2. The flat pipe 1 was bent into a ring shape on the wide sides 10, with an approximately circular ring-shaped form being shown in the exemplary embodiment, although the form can be adapted to almost any shape. A favorable manufacturing process for the heat exchanger provides that a straight flat pipe 1 is first joined to a lamina 2. There can be an inner insert in flat pipe 1, in accordance with the left-hand illustration a in FIG. 2. The middle illustration b is intended to be an extruded multi-chamber pipe, and the right-hand illustration c is a flat pipe with an inner flange.

An end chamber 30 is attached at each end of flat pipe 1, as well as an inlet connection 31 on the one end chamber 30 and an outlet connection 32 on the other end chamber 30. However, depending on the intended flow-through pattern of flat pipe 1, a single end chamber 30 with a partition could also be provided at one end of flat pipe 1. The other end of flat pipe 1 would then simply be closed, with an outbound path and a return path then being design for the first coolant. A lamina 2 is then placed on a wide side 10 of flat pipe 1. In addition, a cover strip 21 likewise of aluminum sheet can be added or mounted on the other side of lamina 2 as a jacket. Cover strip 21 runs approximately parallel to the wide sides 10 of flat pipe 1, and it has numerous openings 20. The construction is next joined together in a brazing process. The construction is then formed into the needed shape essentially by bending, by means of a known stretch bending method. FIG. 3 shows a heat exchanger with an approximately circular shape. The shape could also be oval, however, or could have extensions, with the stretch bending process being augmented by appropriate work steps in order to create the extensions (not shown).

FIG. 1 depicts a detail from the overall construction, from which part of the housing 4 and also part of the rotating machine element 3 can be recognized. Housing 4 surrounds rotating machine element 3. The heat exchanger has been inserted into housing 4 and attached. The wide side 10 facing inward, on which the lamina 2 and (in the exemplary embodiment) also the sheet metal covering 21 are located, faces rotating machine element 3.

The inlet and outlet connections 31, 32 for the first coolant can be connected outside of housing 4 to a hose connection or the like (not shown). Also not shown is an oil sump, into which rotating machine element 3 is immersed. The oil is the second coolant, which cools rotating machine element 3. The oil is flung away by the rotation, which is shown by way of suggestion in FIG. 1 by means of just a few drops 12. The oil to be cooled flows through the openings 20 into the chamber in which the lamina 2 is located, is cooled intensively, and then flows down again into the sump (not shown).

On the end chambers 30 are straps 33, which can be connected to each other so that a relatively stable heat exchanger construction results. For details about this point see FIGS. 4 and 5. The connection between the straps 33 can be made for example by means of clinching. Such connections are known by specialists in the field as TOX connections. The two straps lie one on top of the other. The material located under the face of the die is then pressed into an undercut in the lower strap. Only two TOX points 35 have been shown. This type of connection is simple, quick and reliable.

FIG. 6 shows the use of a lamina from the area of oil cooling in use as the rippled lamina 2. In the illustration on the left the arrangement of the ripples runs in the horizontal direction. In the middle illustration the ripples run vertically, i.e., in the direction of extension of flat pipe 1. In the illustration on the right the direction of the ripples has been shown skewed by about 45° from the longitudinal direction. Simple and inexpensive measures like these can be used to influence the exchange of heat in a desired manner. FIG. 7 shows three exemplary illustrations that differ in the shape and arrangement of the openings 20. The proportion of area of the openings 20 relative to the rest of the jacket 21 also differs. The intent is to cause the oil to remain in contact with lamina 2 and flat pipe 1 for a longer time. 

1. Heat exchanger comprising at least one pipe (1) and at least one lamella (2), for exchanging heat between a first coolant that flows through the pipe (1) and a second coolant that wets the heat exchanger under the influence of centrifugal forces in order to be cooled and to be available to further cool a rotating machine element (3) that is situated in a housing (4), where the heat exchanger is of approximately ring-shaped design, essentially surrounds the rotating machine element (3) and is integrated into the housing (4).
 2. Heat exchanger according to claim 1, characterized in that the at least one pipe (1) is a flat pipe that is bent on its long sides (10), where the lamina (2) is attached to the wide side facing inward, and where the wide sides (10) are situated approximately parallel to the axis of rotation (R).
 3. Heat exchanger according to claims 1 and 2, characterized in that the lamina (2) is provided with a jacket (21) provided with openings (20), that extends approximately parallel to the wide side (10) of the flat pipe.
 4. Heat exchanger according to claim 3, characterized in that the openings (20) are designed and situated so that the second coolant can flow as far as the lamina (2) and as far as the wide side (10) of the flat pipe, and can flow out of the lamella (2) again.
 5. Heat exchanger according to one of the preceding claims, characterized in that the second coolant flows into a sump or similar collecting pan, in which it can be reached by the rotating machine element.
 6. Heat exchanger according to one of the preceding claims, characterized in that an end chamber (30) for supplying and removing the first coolant is situated at one end of the at least one flat pipe (1).
 7. Heat exchanger according to one of the preceding claims 1-5, characterized in that end chambers (30) are situated at both ends of the at least one flat pipe (1).
 8. Heat exchanger according to claim 7, characterized in that straps or similar connecting elements are situated on at least one of the end chambers (30) in order to join the two end chambers (30) together.
 9. Heat exchanger according to one of the preceding claims, characterized in that the at least one flat pipe (1), in which the first coolant flows, is either a soldered or welded flat pipe (1) with an inner insert or a flat pipe manufactured by means of an extrusion process.
 10. Heat exchanger according to one of the preceding claims, characterized in that the lamina (2) has a rippled contour, with numerous cuts at offset positions in the ripple flanks, with the ripples running perpendicular or obliquely to the direction of extension of the pipe (1).
 11. Method for producing a heat exchanger from at least one flat pipe and at least one lamina, according to one of the preceding claims, with the following procedural steps: a) a lamella (2) is placed on the wide side (10) of the at least one flat pipe (1), b) end chambers (30) are affixed to the end of the flat pipe (1), c) the parts are joined by metal material, d) a bending procedure is performed in order to produce a ring-shaped heat exchanger, e) the ring-shaped heat exchanger is inserted into a housing (4) in order to cool the coolant for a rotating machine element (3).
 12. Method according to claim 11, characterized in that step a) includes placing a jacket (21) provided with openings on the lamina (2).
 13. Method according to claims 11 or 12, characterized in that the end chambers (30) are joined together as needed. 